Thumping noise when boiler starts in thr morning

[sturow]

When the boiler starts in the morning,on water only after about 10 minutes a thumping sound starts. It sounds like it is coming from the hot water tank or above in the loft. The noise lasts for about 20-30 seconds then stops. This procedure occurs for about half an hour when the pump is timed to start for the radiators. The thumping seems to stop after this. I have drained down the system and added some descaleing solution(on advise)and bled the radiators. This seemed to quell the noise after about two days but never totally. It is now getting louder again. I have a baxi back boiler which is gas fired and the system (I am led to believe) is gravity fed. Being woke up at 4 in the morning is becoming tiresome,we are thinking about starting a family to have a genuine reason to be awake. Any suggestions will all be very warmly received.

 

[ChrisR]

Can be a number of things but from your info it looks like it's still scale in the boiler, or sludge in the system. Try som e more descaler . You can just put it in the small header tank, it will get into the system via what can be a scaled-up route. No need to drain, though you could let a few litres out of a drain ppe if you want to get the agent in quicker.

If no change then its a poer flush, with more chemicals. Other possibilities should be check when your boiler gets serviced. This type of boiler has the most need to be serviced annually or more frequently if you have fluffy/hairy pets.